This application is based on Application No. 2000-316515, filed in Japan on Oct. 17, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an automotive alternator in which a heat-generating portion is cooled by a liquid coolant.
2. Description of the Related Art
Heat-generating parts such as a rotor winding, a stator winding, a rectifier, and a voltage regulator are mounted in automotive alternators, and to achieve high performance, it is important to suppress temperature increases in the stator winding by efficiently dissipating heat generated, particularly in the stator winding, which is the largest heat-generating part.
It has been proposed conventionally, in Japanese Patent Examined Publication No. HEI 5-16261, for example, that temperature increases in a stator winding in an automotive alternator be suppressed by constructing a distribution channel for a liquid coolant such as water, etc., inside a bracket, filling an electrically-insulating filler composed of a synthetic resin, etc., between a coil end group of the stator winding and the bracket, transferring heat generated in the stator winding to the bracket by means of the electrically-insulating filler, and allowing the heat to be absorbed by the liquid coolant flowing through the distribution channel inside the bracket.
It has also been proposed in Japanese Patent No. 2842500, for example, that temperature increases in a stator winding be suppressed by embedding a tube inside a bracket, the tube constituting a distribution channel for a liquid coolant such as water, etc., extending a portion of the tube out from the bracket, placing the tube in close contact with a coil end group of the stator winding, and allowing heat generated in the stator winding to be absorbed by the liquid coolant flowing through the inside of the tube.
Now the construction of a conventional stator will be explained with reference to FIG. 23.
As shown in FIG. 23, a stator 100 is constituted by a cylindrical stator core 101 composed of a laminated core formed with slots 101a extending axially at a predetermined pitch in a circumferential direction, and a stator winding 102 installed in the stator core 101.
The stator winding 102 is composed of three stator winding phase portions. Each of the stator winding phase portions is manufactured into a generally cylindrical winding assembly by winding one strand of slender copper wire a predetermined number of times into a wave winding at a pitch of three slots, the slender copper wire having a circular cross section coated with electrical insulation. These three winding assemblies are offset from each other at a pitch of one slot in a circumferential direction, and are stacked radially in three layers. Then, the stator 100 is manufactured by reducing the diameter of the three winding assemblies, inserting the three winding assemblies into the stator core 101, and then pressing the three winding assemblies into the slots 101a from a slot opening side.
In the conventional stator 100 manufactured in this manner, because the winding assemblies constituting the stator winding 102 are reduced in diameter and inserted into the stator core 101, and in addition are pressed into the slots 101a from the slot opening side, coil ends composed of bundles of the slender copper wires led out from first slots 110a and led into second slots 110a three slots away are deformed, and in addition the coil ends overlap radially at outlet portions where the coil ends are led out of the slots 110a (or inlet portions where the coil ends are led into the slots). As a result, outer circumferential surfaces of coil end groups of the stator winding 102 have large irregularities in a circumferential direction. Because the positions of the slender copper wires in the coil ends are not specified, large irregularities occur on surfaces of the coil ends. In addition, because the coil ends are formed into bundles of slender copper wires, the slender copper wires are not in close contact with each other in the coil ends, making thermal conductivity in the coil ends poor.
When the cooling construction proposed in Japanese Patent Examined Publication No. HEI 5-16261 is adopted in an automotive alternator mounted with the stator 100 constructed in this manner, the outer circumferential surfaces of the coil end groups and the electrically-insulating filler are in partial contact. Because the outer circumferential surfaces of the coil end groups have irregularities in a circumferential direction, and in addition, the surfaces of the coil ends have irregularities, heat generated in the stator winding 102 is mainly transferred to the electrically-insulating filler via two heat transfer pathways which are directly from the slender copper wires in the coil ends and by means of air in gaps between the slender copper wires and the electrically-insulating filler, and is additionally transferred to the bracket and absorbed by the liquid coolant, cooling the stator 100.
When the cooling construction proposed in Japanese Patent No. 2842500 is adopted in an automotive alternator mounted with this stator 100, the outer circumferential surfaces of the coil end groups and the tube are in partial contact. Because the outer circumferential surfaces of the coil end group have irregularities in a circumferential direction, and in addition the surfaces of the coil ends have irregularities, heat generated in the stator winding 102 is mainly transferred to the tube via two heat transfer pathways which are directly from the slender copper wires in the coil ends and by means of air in gaps between the slender copper wires and the tube, and is absorbed by the liquid coolant, cooling the stator 100.
In conventional automotive alternators, because the outer circumferential surfaces of the coil end groups of the stator winding 102 have large irregularities, and in addition the surfaces of the coil ends have large irregularities, one problem has been that thermal contact between the slender copper wires which constitute the coil end groups and the electrically-insulating filler or the tube is insufficient when the cooling constructions proposed in Japanese Patent Examined Publication No. HEI 5-16261 or Japanese Patent No. 2842500 are adopted, and therefore sufficient cooling cannot be achieved. In addition, because the slender copper wires are not in close contact with each other in the coil ends, another problem has been that thermal conductivity in the coil ends is poor and a sufficient cooling effect cannot be achieved.
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling temperature increases in a stator to be suppressed by constituting a predetermined region of outer surfaces of coil ends in a radial direction of a stator core facing radially outwards from the stator core and extending from a vicinity of the end surface of the stator core to apex portions into a circumferentially-smooth heat-conducting surface to raise thermal contact between the coil ends and a heat-conducting filler or between the coil ends and a tube and to achieve a superior cooling effect.
In order to achieve the above object, according to one aspect of the present invention, there is provided an automotive alternator including:
a stator having a stator core formed with slots extending axially at a predetermined pitch in a circumferential direction and a stator winding installed in the stator core;
a rotor rotatably disposed on an inner circumferential side of the stator; and
a bracket for supporting the stator and the rotor,
wherein a coil end group of the stator winding is constructed such that coil ends folded back outside the slots at an end surface of the stator core are arranged circumferentially,
wherein a predetermined region of outer surfaces of the coil ends in a radial direction of the stator core constitutes a circumferentially-smooth heat-conducting surface, the outer surfaces facing radially outwards from the stator core and extending from a vicinity of the end surface of the stator core to apex portions of the coil ends, and
wherein a distribution channel for a liquid coolant is disposed for absorbing heat generated in the stator and conducted from the heat-conducting surface.
The distribution channel may be formed inside the bracket, a thermally-conductive resin being filled between the coil end group and the bracket in a state of general contact with the heat-conducting surface.
The distribution channel may be constituted by a tube composed of a thermally-conductive material, a portion of the tube being disposed in a state of general contact with the heat-conducting surface of the coil end group.
The stator winding may be provided with a plurality of winding sub-portions each constructed by installing a strand of wire at intervals of a predetermined number of slots so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots, turn portions of the strands of wire which are folded back outside the slots at the end surface of the stator core forming the coil ends and lining up generally uniformly in a circumferential direction to constitute the coil end group.
The turn portions may be disposed circumferentially so as to line up in a plurality of rows radially, radially-adjacent turn portions being in general contact with each other.
The strand of wire may be formed with a rectangular cross-sectional shape, the heat-conducting surface being constituted by a flat side surface of the strand of wire.
The turn portions may be disposed circumferentially such that intermediate portions of the turn portions are in close proximity with each other, the intermediate portions being between portions where the turn portions extend out from the slots and portions where the turn portions are folded back.
A resin may be filled between the turn portions such that a surface of the resin is positioned in a common plane with a surface of the strand of wire, the heat-conducting surface being constituted by a smooth surface composed of the surface of the strand of wire and the surface of the resin.
The strand of wire may be a continuous wire.